The Children?s Heart Program of South Carolina is a statewide consortium of pediatric cardiologists, who care for 90% of the 3.7 million residents in the state. This consortium has all the critical elements for a center in the proposed research network: adequate patient volume, clinical research infrastructure, a track record of subject enrollment, and a demonstrated dedication to hypothesis driven clinical research. The applicant center, MUSC, is the tertiary referral center for the Children?s Heart Program. Current MUSC faculty have participated as PI?s in a total of 20 multicenter clinical trials or registries (10 open, 2 under IRB review). The PI of this application has been the lead investigator nationally in 4 of the 20. These protocols range from industry sponsored drug or device trials, to an NIH sponsored drug trial for fetal heart block, to an NIH prospective registry. The faculty also currently runs 11 local clinical research protocols. Participation in all of these protocols is supported by a dedicated pediatric cardiac research support group with 2 full time RN coordinators and an additional RN FTE. The combined resources of high volume and strong research infrastructure have enabled the PI?s at MUSC to be one of the top 2 subject recruiters in 6 of the 18 completed or active multicenter studies. As requested, the proposal contains a short-term and a long-term protocol. Short-Term. Randomized Trial of Aortopulmonary Collateral Coil Occlusion Prior to Fontan. Multiple factors influence morbidity and mortality for single ventricle patients undergoing Fontan operation. One considered recently is the presence of APC?s. However, multiple retrospective studies have failed to clearly delineate the role of APC?s or their optimum management. This protocol will prospectively evaluate the role of APC?s in postoperative Fontan hemodynamics and morbidity, and determine the importance of preoperative coil embolization in their management. Long-Term. Randomized Trial of Amiodarone vs Cooled- Tip Catheter Ablation for Treatment of Recurrent Intra-atrial Reentry Tachycardia (IART) in Patients with Congenital Heart Disease. IART, the single largest cause of morbidity late after repair of congenital heart disease, is often life-threatening, frustrating to treat and has no clearly superior therapy. This protocol will prospectively compare the most successful medical and catheter therapies for IART. The primary endpoint during a minimum of 2 years follow-up will be IART recurrence after successful ablation, or after drug loading and cardioversion.